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For six years now, John Key's enemies have hunted for ways to dent his armour, remove the sheen and strip back the Teflon.

It is a simple formula — take out Key and you take out National.

And so far this campaign there's been all sorts of tricks to get to Key — "F-John Key" chants, anti-Semitic graffiti, the clever blues song Planet Key and even a burning effigy. None of those really worked and, as usual, Key has charged on through.

But it turns out the thing that could hurt Key, one of his worst enemies, is actually within. It comes in the form of Jason Ede, Key's senior staffer.